Yichen Wang <yichen.w...@bytedance.com> writes:
> From: Hao Xiang <hao.xi...@linux.dev>
>
> During live migration, if the latency between sender and receiver is
> high and bandwidth is also high (a long and fat pipe), using a bigger
> packet size can help reduce migration total time. The current multifd
> packet size is 128 * 4kb. In addition, Intel DSA offloading performs
> better with a large batch task.
Last time we measured, mapped-ram also performed slightly better with a
larger packet size:
2 MiB 1 MiB 512 KiB 256 KiB 128 KiB
AVG(10) 50814 50396 48732 46423 34574
DEV 736 552 619 473 1430
>
> This change adds an option to set the packet size, which is also useful
> for performance tunin. Both sender and receiver needs to set the same
> packet size for things to work.
>
> Set the option:
> migrate_set_parameter multifd-packet-size 4190208
>
> Signed-off-by: Hao Xiang <hao.xi...@linux.dev>
> Signed-off-by: Yichen Wang <yichen.w...@bytedance.com>
> ---
> migration/migration-hmp-cmds.c | 7 +++++++
> migration/multifd-zlib.c | 6 ++++--
> migration/multifd-zstd.c | 6 ++++--
> migration/multifd.c | 6 ++++--
> migration/multifd.h | 3 ---
> migration/options.c | 38 ++++++++++++++++++++++++++++++++++
> migration/options.h | 1 +
> qapi/migration.json | 21 ++++++++++++++++---
> 8 files changed, 76 insertions(+), 12 deletions(-)
>
> diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
> index c422db4ecd..27ba0ce79a 100644
> --- a/migration/migration-hmp-cmds.c
> +++ b/migration/migration-hmp-cmds.c
> @@ -292,6 +292,9 @@ void hmp_info_migrate_parameters(Monitor *mon, const
> QDict *qdict)
> monitor_printf(mon, "%s: %u ms\n",
> MigrationParameter_str(MIGRATION_PARAMETER_X_CHECKPOINT_DELAY),
> params->x_checkpoint_delay);
> + monitor_printf(mon, "%s: %" PRIu64 "\n",
> + MigrationParameter_str(MIGRATION_PARAMETER_MULTIFD_PACKET_SIZE),
> + params->multifd_packet_size);
> monitor_printf(mon, "%s: %u\n",
> MigrationParameter_str(MIGRATION_PARAMETER_MULTIFD_CHANNELS),
> params->multifd_channels);
> @@ -576,6 +579,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict
> *qdict)
> p->has_dsa_accel_path = true;
> visit_type_strList(v, param, &p->dsa_accel_path, &err);
> break;
> + case MIGRATION_PARAMETER_MULTIFD_PACKET_SIZE:
> + p->has_multifd_packet_size = true;
> + visit_type_size(v, param, &p->multifd_packet_size, &err);
> + break;
> case MIGRATION_PARAMETER_MULTIFD_CHANNELS:
> p->has_multifd_channels = true;
> visit_type_uint8(v, param, &p->multifd_channels, &err);
> diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
> index 2ced69487e..bd900fe575 100644
> --- a/migration/multifd-zlib.c
> +++ b/migration/multifd-zlib.c
> @@ -49,6 +49,7 @@ static int zlib_send_setup(MultiFDSendParams *p, Error
> **errp)
> struct zlib_data *z = g_new0(struct zlib_data, 1);
> z_stream *zs = &z->zs;
> const char *err_msg;
> + uint64_t multifd_packet_size = migrate_multifd_packet_size();
>
> zs->zalloc = Z_NULL;
> zs->zfree = Z_NULL;
> @@ -58,7 +59,7 @@ static int zlib_send_setup(MultiFDSendParams *p, Error
> **errp)
> goto err_free_z;
> }
> /* This is the maximum size of the compressed buffer */
> - z->zbuff_len = compressBound(MULTIFD_PACKET_SIZE);
> + z->zbuff_len = compressBound(multifd_packet_size);
> z->zbuff = g_try_malloc(z->zbuff_len);
> if (!z->zbuff) {
> err_msg = "out of memory for zbuff";
> @@ -200,6 +201,7 @@ out:
> */
> static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
> {
> + uint64_t multifd_packet_size = migrate_multifd_packet_size();
> struct zlib_data *z = g_new0(struct zlib_data, 1);
> z_stream *zs = &z->zs;
>
> @@ -214,7 +216,7 @@ static int zlib_recv_setup(MultiFDRecvParams *p, Error
> **errp)
> return -1;
> }
> /* To be safe, we reserve twice the size of the packet */
> - z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
> + z->zbuff_len = multifd_packet_size * 2;
> z->zbuff = g_try_malloc(z->zbuff_len);
> if (!z->zbuff) {
> inflateEnd(zs);
> diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
> index ca17b7e310..8aaa7363be 100644
> --- a/migration/multifd-zstd.c
> +++ b/migration/multifd-zstd.c
> @@ -49,6 +49,7 @@ struct zstd_data {
> */
> static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
> {
> + uint64_t multifd_packet_size = migrate_multifd_packet_size();
> struct zstd_data *z = g_new0(struct zstd_data, 1);
> int res;
>
> @@ -68,7 +69,7 @@ static int zstd_send_setup(MultiFDSendParams *p, Error
> **errp)
> return -1;
> }
> /* This is the maximum size of the compressed buffer */
> - z->zbuff_len = ZSTD_compressBound(MULTIFD_PACKET_SIZE);
> + z->zbuff_len = ZSTD_compressBound(multifd_packet_size);
> z->zbuff = g_try_malloc(z->zbuff_len);
> if (!z->zbuff) {
> ZSTD_freeCStream(z->zcs);
> @@ -188,6 +189,7 @@ out:
> */
> static int zstd_recv_setup(MultiFDRecvParams *p, Error **errp)
> {
> + uint64_t multifd_packet_size = migrate_multifd_packet_size();
> struct zstd_data *z = g_new0(struct zstd_data, 1);
> int ret;
>
> @@ -209,7 +211,7 @@ static int zstd_recv_setup(MultiFDRecvParams *p, Error
> **errp)
> }
>
> /* To be safe, we reserve twice the size of the packet */
> - z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
> + z->zbuff_len = multifd_packet_size * 2;
> z->zbuff = g_try_malloc(z->zbuff_len);
> if (!z->zbuff) {
> ZSTD_freeDStream(z->zds);
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 014fee757a..87ed421364 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -1189,7 +1189,8 @@ bool multifd_send_setup(Error **errp)
> MigrationState *s = migrate_get_current();
> Error *local_err = NULL;
> int thread_count, ret = 0;
> - uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
> + uint32_t page_count =
> + migrate_multifd_packet_size() / qemu_target_page_size();
> bool use_packets = multifd_use_packets();
> uint8_t i;
>
> @@ -1600,7 +1601,8 @@ static void *multifd_recv_thread(void *opaque)
> int multifd_recv_setup(Error **errp)
> {
> int thread_count;
> - uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
> + uint32_t page_count =
> + migrate_multifd_packet_size() / qemu_target_page_size();
> bool use_packets = multifd_use_packets();
> uint8_t i;
> int ret;
> diff --git a/migration/multifd.h b/migration/multifd.h
> index 871e3aa063..63cec33c61 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -44,9 +44,6 @@ MultiFDRecvData *multifd_get_recv_data(void);
> #define MULTIFD_FLAG_QPL (4 << 1)
> #define MULTIFD_FLAG_UADK (8 << 1)
>
> -/* This value needs to be a multiple of qemu_target_page_size() */
> -#define MULTIFD_PACKET_SIZE (512 * 1024)
> -
> typedef struct {
> uint32_t magic;
> uint32_t version;
> diff --git a/migration/options.c b/migration/options.c
> index f839493016..1417fa6ab0 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -73,6 +73,12 @@
> #define DEFAULT_MIGRATE_ANNOUNCE_ROUNDS 5
> #define DEFAULT_MIGRATE_ANNOUNCE_STEP 100
>
> +/*
> + * Parameter for multifd packet size.
> + */
> +#define DEFAULT_MIGRATE_MULTIFD_PACKET_SIZE (128 * 4 * 1024)
> +#define MAX_MIGRATE_MULTIFD_PACKET_SIZE (1023 * 4 * 1024)
Why 1023?
> +
> #define DEFINE_PROP_MIG_CAP(name, x) \
> DEFINE_PROP_BOOL(name, MigrationState, capabilities[x], false)
>
> @@ -167,6 +173,9 @@ Property migration_properties[] = {
> /* parameters.dsa_accel_path, qdev_prop_string, char
> *), */
> /* DEFINE_PROP_STRING("dsa-accel-path", MigrationState, */
> /* parameters.dsa_accel_path), */
> + DEFINE_PROP_SIZE("multifd-packet-size", MigrationState,
> + parameters.multifd_packet_size,
> + DEFAULT_MIGRATE_MULTIFD_PACKET_SIZE),
>
> /* Migration capabilities */
> DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> @@ -777,6 +786,13 @@ int migrate_multifd_channels(void)
> return s->parameters.multifd_channels;
> }
>
> +uint64_t migrate_multifd_packet_size(void)
> +{
> + MigrationState *s = migrate_get_current();
> +
> + return s->parameters.multifd_packet_size;
> +}
> +
> MultiFDCompression migrate_multifd_compression(void)
> {
> MigrationState *s = migrate_get_current();
> @@ -898,6 +914,8 @@ MigrationParameters *qmp_query_migrate_parameters(Error
> **errp)
> params->downtime_limit = s->parameters.downtime_limit;
> params->has_x_checkpoint_delay = true;
> params->x_checkpoint_delay = s->parameters.x_checkpoint_delay;
> + params->has_multifd_packet_size = true;
> + params->multifd_packet_size = s->parameters.multifd_packet_size;
> params->has_multifd_channels = true;
> params->multifd_channels = s->parameters.multifd_channels;
> params->has_multifd_compression = true;
> @@ -957,6 +975,7 @@ void migrate_params_init(MigrationParameters *params)
> params->has_max_bandwidth = true;
> params->has_downtime_limit = true;
> params->has_x_checkpoint_delay = true;
> + params->has_multifd_packet_size = true;
> params->has_multifd_channels = true;
> params->has_multifd_compression = true;
> params->has_multifd_zlib_level = true;
> @@ -1038,6 +1057,19 @@ bool migrate_params_check(MigrationParameters *params,
> Error **errp)
>
> /* x_checkpoint_delay is now always positive */
>
> + if (params->has_multifd_packet_size &&
> + ((params->multifd_packet_size < DEFAULT_MIGRATE_MULTIFD_PACKET_SIZE)
> ||
> + (params->multifd_packet_size > MAX_MIGRATE_MULTIFD_PACKET_SIZE)
> ||
> + (params->multifd_packet_size % qemu_target_page_size() != 0))) {
> + error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
> + "multifd_packet_size",
> + "an integer in the range of "
> + stringify(DEFAULT_MIGRATE_MULTIFD_PACKET_SIZE)
> + " to "stringify(MAX_MIGRATE_MULTIFD_PACKET_SIZE)", "
> + "and must be a multiple of guest VM's page size.");
> + return false;
> + }
> +
> if (params->has_multifd_channels && (params->multifd_channels < 1)) {
> error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
> "multifd_channels",
> @@ -1219,6 +1251,9 @@ static void
> migrate_params_test_apply(MigrateSetParameters *params,
> dest->x_checkpoint_delay = params->x_checkpoint_delay;
> }
>
> + if (params->has_multifd_packet_size) {
> + dest->multifd_packet_size = params->multifd_packet_size;
> + }
> if (params->has_multifd_channels) {
> dest->multifd_channels = params->multifd_channels;
> }
> @@ -1344,6 +1379,9 @@ static void migrate_params_apply(MigrateSetParameters
> *params, Error **errp)
> colo_checkpoint_delay_set();
> }
>
> + if (params->has_multifd_packet_size) {
> + s->parameters.multifd_packet_size = params->multifd_packet_size;
> + }
> if (params->has_multifd_channels) {
> s->parameters.multifd_channels = params->multifd_channels;
> }
> diff --git a/migration/options.h b/migration/options.h
> index 78b9e4080b..b37cffc887 100644
> --- a/migration/options.h
> +++ b/migration/options.h
> @@ -86,6 +86,7 @@ const char *migrate_tls_hostname(void);
> uint64_t migrate_xbzrle_cache_size(void);
> ZeroPageDetection migrate_zero_page_detection(void);
> const strList *migrate_dsa_accel_path(void);
> +uint64_t migrate_multifd_packet_size(void);
>
> /* parameters helpers */
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index ff41780347..1a9dc5d74c 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -839,6 +839,10 @@
> # only has effect if the @mapped-ram capability is enabled.
> # (Since 9.1)
> #
> +# @multifd-packet-size: Packet size in bytes used to migrate data.
> +# The value needs to be a multiple of guest page size.
> +# The default value is 524288 and max value is 4190208. (Since 9.2)
> +#
> # Features:
> #
> # @unstable: Members @x-checkpoint-delay and
> @@ -864,7 +868,8 @@
> 'vcpu-dirty-limit',
> 'mode',
> 'zero-page-detection',
> - 'direct-io'] }
> + 'direct-io',
> + 'multifd-packet-size'] }
>
> ##
> # @MigrateSetParameters:
> @@ -1020,6 +1025,10 @@
> # only has effect if the @mapped-ram capability is enabled.
> # (Since 9.1)
> #
> +# @multifd-packet-size: Packet size in bytes used to migrate data.
> +# The value needs to be a multiple of guest page size.
> +# The default value is 524288 and max value is 4190208. (Since 9.2)
> +#
> # Features:
> #
> # @unstable: Members @x-checkpoint-delay and
> @@ -1061,7 +1070,8 @@
> '*mode': 'MigMode',
> '*zero-page-detection': 'ZeroPageDetection',
> '*direct-io': 'bool',
> - '*dsa-accel-path': ['str'] } }
> + '*dsa-accel-path': ['str'],
> + '*multifd-packet-size' : 'uint64'} }
>
> ##
> # @migrate-set-parameters:
> @@ -1231,6 +1241,10 @@
> # only has effect if the @mapped-ram capability is enabled.
> # (Since 9.1)
> #
> +# @multifd-packet-size: Packet size in bytes used to migrate data.
> +# The value needs to be a multiple of guest page size.
> +# The default value is 524288 and max value is 4190208. (Since 9.2)
> +#
> # Features:
> #
> # @unstable: Members @x-checkpoint-delay and
> @@ -1269,7 +1283,8 @@
> '*mode': 'MigMode',
> '*zero-page-detection': 'ZeroPageDetection',
> '*direct-io': 'bool',
> - '*dsa-accel-path': ['str'] } }
> + '*dsa-accel-path': ['str'],
> + '*multifd-packet-size': 'uint64'} }
>
> ##
> # @query-migrate-parameters:
